of stockholm



Reued May 31, 1932 PATENT foFFlcE ALI' LYSHOLH, OF STOCKHOLM, BWDEN", ASSIGNQB. TO AKTIEBOLAGET LJ'UNGSTRMB ANGTURBIN, F STOCKHOLM, SWEDEN, A JOINT-STOCK COMPANY BLADE SYSTEM FOB. T'UBBINES `Original No. 1,777,098, dated September 30, 1930, Serial No. 287,176, led June 21, 1928, and in Sweden June 30, 1927. Application for reissue led February 17, 1932. Serial No. 593,673.

The present invention relates primarily to certain improvements in blade systems for gas or steam turbines, the invention having for its primary object to bring about a reduction of the total number of blades required in a turbine.

A characteristic combination of features of the invention is that the thickness of each blade is greater at the inlet sideor` the blade l0 than at the outlet side thereof, and that the blade pitch is related to the height of the blades as kin/Sill a,

k 0.5 and a designates the outlet angle of the blade. By

the height of the blades is meant the dimension in the general direction of flow of the 0 driving Huid relative to the'blades, as represented by the dimension E in Fig. 1. v

A urther characteristic combination of features according to the invention is that the maximum thickness of each blade is on Where A further and generally more specific characteristic combination of features is that the thickness of each blade is greater at the inlet side of the blade than at the outlet side thereof, and that the blade pitch is 0.9 to 1.2 times the dimension E of the blades.

A further characteristic combination of features of generally more specific nature is that the maximum thickness of each blade is c-n the inlet side of the line of gravity of the blade and thence decreases toward the outlet side, and thatthe blade pitch is 0.9 to 1.2 times the dimension E of the blades.

A still further characteristic combination of features, of generally more specitic nature is that each blade has a rounded shape toward the incoming driving fluid, and that the blade pitch is 0.9 to 1.2 times the dimension of the blades, measured in the direction of flow o the driving fluid.

Other and more detailed characteristics of blading embodying the invention will be pointed out in the ensuing description and in the appended claims.

The feature of providing rounded inlet edges in the blades of elastic iiuid turbines, and of thus imparting to the blades a streamline contour to increase the eiieiency of the individual blades, is known to be previously suggested in the art of turbine design, Whereas the combined features of rounding the inlet edges of the blades or of locating the maximum thickness of each individual blade to the inlet side of the blade, and of providing a blade pitch which is related to the height of the blades as Ich/Sin a,

k. 0.5 and a where which more specifically is 0.9 to 1.2 times the height of the blades, are novel and charac,

teristic of my present invention, to the best of my knowledge and belief.

In the acompanying drawing, Fig. 1 replet surfaces resents a cross-section of one of the blades of the improved blade system according to the invention.- Figs. 2 and 3 show a few blades of the type involved in the present invention and spaced in a manner falling within the scope of the invention.

With reference to Fig. 1 of thedrawing, A denotes the center of gravit of the blade, while Bis the center line of t e blade. This center lineis divided into three equal parts,

Y and through the dividing points intersecting lines C and D are drawn at right angles to the center line. E is the height of the blade, that is to say, its dimension measured in the general direction of flow of the driving Huid, this direction being axial in an axial-flow turbine and radial in a radial-How turbine. a designates the outlet angle of the blade.

As will be clearly seen, the greatest thickness of the blade is on the inlet side of the blade, the said thickness being located in front of the center of gravity A.

It will also be observed that the center of ravity A is nearer to the inlet side of the lade than to the outlet side thereof. This is due tothe facttthat the blade is of substantially greater thickness adjacent to its inlet side, as compared with its maximum thickness, than are blades of usual profile.

From the drawings it will be evident that blades of the character contemplated by my invention have profiles providing blades with generally rounded inlet surfaces and with concave and convex side surfaces. With such blades the'concave side surfaces and the injoin or merge along lines arallel to the longitudinal axes of the bla es, at which lines the blade surfaces change from concave surfaces to surfaces which are generally convex. Such lines may conveniently be termed lines of reverse curvature.

I have found that in order to utilize to the v fullest extent the potential advantages of my invention, each blade should be of the general shape illustrated, in that the thickness of the blade at theline of reverse curvature, which it will be observed is adiacent to the inlet side of the blade, is equal to at least a major portion of the maximum blade thickness and may in some instances be equal to or constitute the maximum blade thickness. In the blade shown in Fig. 1,'the blade thickness at' the line of reverse curvature is substantially the sameas the maximum blade thickness, and in the blades shown in Figs. 2 and 3 the blade thickness at the line of .reverse curvature is w,ell over fifty per cent of the maximum blade thickness. v

With the mass of the blade so distributed, Iy have discovered that the most suitable range of pitch ratios of the turbine blading, that is to say, the most suitable values of distance between the blades, as compared with the height of the blades, having regard to the outlet angles, will be obtained if the pitch is related to the height of the blades as ,tf1/Sin a Where k' 0.5, as will hereinafter be more fully explained.

In eneral it may be said that with a given lade profile the Vproper pitch between blades is different for different values of the outlet angle a of the bladingand I have therefore provided means for defining the pitch characteristic of the present invention in such manner asto take into account the several values of the outlet angle a which may be employed. This means for defining the invention comprises the hereinbefore stated formula in which the ratio of the pitch of the blading with respect to the height of the blades in the direction of the flow of fluid therethrough is equal to the ratio of` a factor .k divided by `1/sin a, the factor k, if the pitch of the blading is to be within the scope of the present invention, being 0.5. It will be evident tha'. by defining this characteristic of the invention through the medium of the formula above set forth, the absolute value of the pitch ratio of the blading for a given value of lc will be different for different values of the outlet angle of the bla-ding, which is the condition existing in actual practice. In other words, the maximum value of the pitch ratio heretofore employed in the prior art is not a constant but is a value varying with variations in the outlet angle of the blading. Likewise, in the exercise of the present invention, the valueof the pitch ratio to be employed in any specific i instance (other factors being equal) depends upon the value of the outlet angle of the specific blading in question. By means of the above stated formula I amenabled to clearly define this characteristic of the present invention and to also clearly distinguish my improvement from the practice of the prior art, while at the same time taking into account variations in the value of the minimum pitch ratio falling within the scope of the present invention, which variations occur because of permissible variations in the outlet angle in the blading.

For example, let us take the case in which the outlet angle of the blading is 20 (which angle is representative/of a normal turbine design) and in which the pitch ratio is unity. Designating the blade pitch as p, and the blade height (dimension E, Fig. 1) asv L, and applying the formula,

formula becomes then becomes Considering the matter from .another angle, let` us determine the minimum pitchv ratio for20 bladingwhichfalls within the scope of the feature of the invention defined by thelformula. The formula .`p/h= .5/1/sin 20.

Solving Vfor p/L Wefind its value to be .855. Following similar procedure We find thatl for 15 blading, the minimum pitch defined by the formula is .984 and "for 25 blading the corresponding value is .77. For abnormally large outlet angles, such for example as 40, the corresponding value is l.624, but as will be appreciated by those skilled in the art, the proper pitch ratiofo'r blading of this eXtreme type, according to the teaching of e the prior art, is 'materially smaller than this 'figure'.

Insofar as I am aware, noblade construcT tion in the prior art has contemplated the use of blading having a pitch as great as 0.9 of the height ofthe blades, regardless `"of the outlet angle employed. A. pitch ratio of about`0.7 represents the maximum em? ploy'ed in ytheprior artw'and this value has heretofore been employed only with blading having smallloutletangles', While blading for larger and moreusual outletan'gles has been used with a I nyairimum pitch ratio ofl materially lsmaller value. The present inven' tion therefore may be further and 'more genverally sp'ecifically'd'eined by the kcombina- I :tion of blading having the profile characteristics herein set forth and a pitch ratio characteristic o'f not less than the absolute value herein given, This-'more limited definition ofthe-invention. relates= more specifically to that portion; otthefield o fturbinedesign represented by blading yhavingoutlet angles Within .the` range. yof What has becomejestablishedi as. normal or usual design..l v

The advantage ,1sy gained through thepres` i ent invention-thata `smaller number of blades are required in the Whole ,turbine than hitherto, the possible reduction-'of the number of bla-.des being, in fact 20.110 40%,vinvolving a lCorrespending reductionfin the cost Vof manu? I facture., f

In Fig.. 2, nina-mtg, a 'blade ys tem `r'acfcqoyrding tothe inventionwhere "the thickness of each blade is greater at the *inlet side'fof" theyblade than Lat the outlet "side" thereof, a path of the driving fluidv l thathasbeen previously required.

betweenthe blades is,v indicatedy b lines g;

Fig. 3 shows how the fluid, t e path. of

which :is indicated by the linesh, h, passes n the same blades as those shown in Fig. 2,

may vary materially ,both with respect vto f velocity and direction, Without the eiiiciency Vof the present blade Asyst-em being appreciably impaired thereby. f

As illustrated, the blades of a blade system according to the invention are given a greater thickness at the inlet side of the bladerow than at the outlet side thereof, and the edges of the blades directed'toward the entering driving luid are rounded on the lines of co'nic curves such as circles, ellipses, parabolas or hyperbolas, or have an approximate.- i'

ly similar shape. yBy thus adopting blades of the shape disclosed in' Figs. 1, Q a-nd 3 for the blade system according Ato the present invention, the furthe-r advantage isl gained, inaddition Vto that of a reduced number of blades, that ythe losses'vvill be comparatively independent of the direction of the incomingr driving fluid.-

Therefore, the efficiency ofthe blade system i will be independent of the variations 'and speed conditions involved by overloading,` reduced loading or a' variable number of revolutionsof the turbine.' Moreover, when systems are suitable in localities Where the percentage of moisturev of the steam is high, inasmuch asthey offer, inthe first place, greater resistance to Wearand,` further-niore,-A

arefsuited' to the,` altered inlet angles under which the moist-ure ofY the tothe blade system.

steam is supplied v -to a greater extent yindependent 'of "theinl'et angle of 'the fluid, it is no longer necessary,-

.steamis used as a driving Huid, such blades; ,1

lil,

I nasmuch as vthe novel-:blade are I.

as is the case in `certain turbines,that. blades ;f

be made in different sizes, for instance with radial dimensionv 'of 5, '7 'o1'f`10 millimeters,

and that each dimension made in l0. di'eryent blade profilessuited todifferent inlet and outlet angles. or, altogether, aboutBO differf ent 'blade profiles. Y. Blade systems ,according 1:, to' thepresent'invention may :be bullt with l blades Sofa single size having a'dilnension of ,l

10 millimeters vin the direction of How of theiuid, and only 2 orlkblade profilesare re-l quired for 'different` directions .and velocities of the fluid. In the standardizationV of tur? binepmanufa-cture with blade systems accord ing to the invention it will lthus only .be neces-` sary to make f7; of thenumberof blade types The above mentioned reduction in the total 0.9 and a second blade profile will be similarly satisfactoryin turbines in which the velocity triangle gives a ratio of u/c of from 0.8 to 1.3. Satisfactory turbines in which the ratio of u/cis anywhere from 0.5 to 1.3

may be built with blading having either one v of *only two'blade profiles.

Furthermore, I have found .that with blades having a. profile and pitch characteristics of the resent invention, satisfactory variable speed turbines, in which the ratio u/c may vary from zero to 1.5 with variations in the speed of the turbine, may be built with blades of one profile.

From the foregoing, it will be seen that, in accordance with the present invention, not more than three blade profiles are required in order to take care of the full range of turbine designs normally encountered, blades,l`

of one profile-being sufficient for variable speed turbines and blades of two different profiles being suliicient for constant speed turbines having normally encountered velocity characteristics.-

On account of the above it may be of advantage, economically, to provide blades milled in their entiretyand inserted directly into the ring bonds unitin the blades in the blade rings, it being then so possible to make the outer blade lengths of radial flow turbines at least 20% longer, whereby the output of the turbine may be increased in a corresponding degree, or, if thesame blade len th is emloyed, while the height of the btade is reuced, the sum of the squares of the blade speeds may be increased. In order to obtain a turbine, for example a back pressure turbine with possibilities of overloading by means of. by-passage while maintaining a good eflciency under all conditions, the relation of the velocity u/c should be great. With a'blade system according to the invention, this relation u/c may be increased to values 0.8, without having to resort to the thin blade profiles of earlier constructions. Moreover, a turbine constructed with-a blade system according to the invention will ob# tain an increased turning moment at the moment of starting, and for this reason such a turbine cn better be used, for instance as 'a motor. for the driving vof locomotives, whereby the capability of the locomotive to force adients is increased.

In e above, I have shown that with blade channels for flow of driving fluid of such excessive width as to have impractical operating characteristics. However, I have indicated, from my studies in connection with locomotive turbines that 1.2 is a reasonable upper limit for such type of load.

While I have particularlydeveloped the blading herein described for steam or gas turbines, the invention is not necessarily restricted to this type of driving fluid.

lVhat I claim is:

1. In a blade system for gas or steam turbines, the combination of the features that the thickness of each blade is reater at the inlet side of the blade than at t e outlet side thereof, and that the blade to the height of the blades as where k 0.5 and less than a value resulting in channels of impractical width and a designates the outlet an le of the blade.

2. In a blade system or gasor steam turbines, the combination of the features that the maximum thickness of each blade is on the inlet side of the center of gravity of the cross section of the blade and thence decreases toward the outlet side, and that the blade pitch is related to the height of the blades Ica/sin a,

pitch lis related where k 2 0.5 and less than a value resulting in channels of impractical width and a designates the outlet angle ofthe blade.

3. In a blade system for gas or steam turbines, the combination of the features that each blade. has a rounded shape toward the incoming steam, and that the blade pitch is related to the height of the blades as where l: g 0.5 arid less than a value resulting in channels of impractical width and a designates the outlet angle, of the blade. A

'4. In a blade system for gas or steam turbines, the combination of the featur that the thickness of each blade is greater at the inlet side of the blade than at the outlet side iis thereof, and that the blade itch is 0.9 to 1.2

times the height of the bla es.

5. In a blade system for gas or steam turbines, the combination of the features that the maximum thicknem of each blade is on the inlet side of the center of ravity of the cross section of the blade and t ence decreases toward the outlet side, and that the blade pitch is 0.9 to 1.2 times the height of the blades.

6. In a blade system for gas or steam turbines. the combination of the features that each blade has a rounded shape toward the incoming driving fluid, and that the blade pitch is 0.9 to 1.2 times the height of the blades.

7 In a blade system for gas or steam turbines, the combination ofthe features that the inlet edge of each blade is of a circular cross-section, and that the blade pitch is related to the height of the blades as kry/Sin a, where k 0.5 and less than a value resulting in channels of impractical Width and a designates the outlet angle of the blade.

8. In a blade system for gas or steam turbines, the combination of the features that the inlet edge of each blade is of a circular cross-section, and that the blade pitch is 0.9 to 1.2 times the height of the blades.'

9. In turbine blading, a row of blades having a blade pitch of at least 0.9 times the height of the blades and less than a value resulting in channels of impractical Width, each blade having a profile comprising approximately a conic curve at the inlet side of the blade row.

10. In turbine blading, a row of blades in which the pitch is related to the height of the blades as kia/Sin a,

Where a is the outlet angle of the blading and 7c 0.5 and less than a value resulting in channels of impractical Width and in which each bladehas a profile comprising approximately a coniccurve at the inlet side of the blade row.

11. In turbine blading, a row of blades in which the pitch is related to the height of the blades as H1/Sin a,

Where a is the outlet angle of the blading and k 0.5 and less than a value'resulting in channels of impractical Width and in which each blade has a profile such that the maximum thickness of the blade is on the inlet side of the center of gravity of the cross section of the blade and the portion of the profile at the inlet side of the blade row approximates a conic curve.

12. In turbine blading, a row of blades having a pitch of at least 0.9 times the height of the blades and in which the pitch is so related to the height of the blades that in the equation p/h Ica/sin a,

: g 0.5 and less than a value resulting in channels of impractical Width, where a is the outlet angle of the blading, and 'leach i blade having a profile such that the maximum thickness of the blade is on the inlet side of the center of gravity of the cross section of the blade and the portion of the profile at the inlet side of the blade row is curved.

13. In a turbine blading, a row of blades having substantially thickened portions adjacent to the inlet side of the row, the lines of the centers of gravity of the cross-sections of the blades being nearer to the inlet side of the row than to the outlet side thereof, the maximum thickness of the blades being nearer to the inlet side of the row than said lines of the centers of gravity, the blades being pitched to provide channels for flow of driving iiuid not exceeding in width a value giving practical operating characteristics to the channels, and the pitch being so related to the height of the blades that 7c 0.5 in ythe equation p/h=k/ sin a Where a is the outlet angle of the blades in the row.

14. In turbine blading, a row of blades having substantially thickened portions adjacent to the inlet side of the row, the lines of the centers of gravity of the cross-sections of the blades being nearer to the inlet side of the row than to the outlet side thereof, the maximum thickness of the blades being nearer to the inlet side of the row than said lines of the centers of gravity, the blades being pitched to provide channels for flow -of driving liuid not exceeding in Width a value giving practical operatingI characteristics to the channels and the blade pitch being equal to at least 0.9 times the height of the blades.

v 15. In turbine blading, a ronr of blades having substantially thickened portions adjacent to the inlet side of the row, the lines of the centers of gravity of the cross-sections of the blades being nearer to the inlet side of the row than to the outlet side thereof, the maximum thickness of the blades being nearer to the inlet side of the row than said lines of the centers of gravity and the blade pitch being 0.9 to 1.2 times the height of the blades.

16. In turbine blading, a row of blades having profiles providing inlet surfaces and concave and convex side surfaces, the thickness of the blades at the lines of reverse curvature Where the inlet surfaces and the concave side surfaces join being equal to at least a major portion of the maximum thickness of the blades, the blades being pitched to provide channels for iiow of driving fluid not exceeding in Width a value giving practical operating characteristics to the channels and the pitch being so related to the height of the blades that k 0.5 in the equation p/h =c/ sin a where a is the outlet angle of the blades in the row.

17. In turbine blading, a. row of blades having profiles providing inlet surfaces and concave and convex side surfaces, the thickness of the blades at the lines of reverse curvature where the inlet surfaces and the concave side surfaces join being equal to at least a major portion of the maximum thickness m of the blades, the blades being pitched to provide channels for flow of driving fluid not exceeding in width a. value givmg practical o rating characteristics to the channels and di); blade pitch being equal to at least 0.9

u times the height of the blades.

18. In turbine blading, a row of blades having profiles providing inlet surfaces and concave and convex side surfaces, the thickness of the blades at the lines of reverse cur- .20 vature where the inlet surfaces and the concave side surfaces join being equal to at least a maj o'r portion of the maximum-thickness of the blades and the blade pitch being 0.9 to 1.2 times the height of the blades.

5 In testimony whereof, I hereunto aix my signature.

ALF LYSHOLM. 

